"It's very easy [for a dress to rip] because you get out of the car, you go up, you try to go to the restroom. When you're on the red carpet, a lot of people step on your dress and pull it," Vergara, 40, told PEOPLE Friday. "After awhile, that's what causes the stitches to get loose because usually you have those long gowns. You can never really control it, but you just hope for the best."